The expected result for this work is push-based executor working for many types of queries (currently we aim at TPC-H), but it's unlikely to be a production-ready patch to commit into mainline at that stage. This work is the actual topic for our student's thesis, so he has already started, and has working prototypes for very simple plans. Also, he won't be working on this alone, but rather will make use of support and experience of our team (as well as mentor's help).
So this is not about replacing current pull executor right away, but rather to develop working prototype to find out about the benefits of switching from pull to push model (for both the interpreter and LLVM JIT).